Home Networking Digital TV based on LnCP

Seungcheon Kim, Jeongae Park, Kyoungwoo Lee and Sangwook Lim.

Digital TV Lab., LG Electronics Inc., Seoul, Korea.

Tel: +822 3497 8759

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ABSTRACT

This paper presents Home Networking Protocol, LnCP, which has been developed to connect home appliances. Then Digital TV that can communicate with other appliances using LnCP is introduced.

INTRODUCTION

So far the transmission technologies for the home networking have been going their ways without concern of each other. Those include the wireless technologies like IEEE802.11, Bluetooth, HomeRF and the wired technologies such as HomePNA, Ethernet (IEEE802.2/3), Power Line Communication (PLC), and IEEE1394. All of them could be the main technologies that can make the infrastructure of the future Home Network. While they have been competing for the best candidate of the home networking, however, they have never tried to resolve the problems that users could feel when they start to utilize the Home Network. Those issues could be referred to understanding, installation, maintenance and use [1], consequently, which means that users want to get some convenience and use their home network easily whatever technologies they use as the lower layer of home network. On top of that, they want to let the legacy appliances connected in their home network rather than the information technology devices. Considering all those user’s requirements, in this paper, we introduce the Home Networking Digital TV (HNTV) that is integrated with the Living Network Control Protocol (LnCP) [2][3] devised by LG Electronics Inc.

LnCP ARCHITECTURE

Devices in LnCP networks are categorized into two types; one is slave and the other is master. It’s only dependent on device’s role in the home network. For example, most people want to control a washing machine watching TV rather than cooking food in front of microwave oven. Therefore, we can call TV as master device in LnCP networks. The main reason to divide LnCP devices is to make the roles of devices in networks simple and light. What slave device should do is to follow the command that is issued by the master device. Thus, master device should know how to control the slave device that user want to control and be able to interpret the command code that is received from slave device.

One of the outstanding features of LnCP is that it’s based on the event-driven communication. To know the status of other devices, there are roughly two methods. One is questioning other devices periodically and the other is notifying the status changes when the changes happen. LnCP adopts the latter one and enables whole devices to be aware of the status updates of other devices by asynchronous notification.

The follow figure shows protocol architecture of LnCP protocol. It consists of four layers and each of their roles is explained as follows.

Fig.1 Protocol Architecture in HNTV

  1. Application Layer

Application layer concerns only Command Code set that is directly used to control and monitor the status of other LnCP devices. Main role of application layer is interpreting command codes and performing the proper action according to the command codes. In addition, in case of master device, it has to provide the interface to the user to get an input or display the result of controlling the devices to the user.

  1. LnCP Layer

LnCP layer takes a role of communicating with other device with packet format. It generates packet as shown in Fig.2. Besides, for reliable communication, it should perform networking functions such as retransmission, error control and flow control etc. Two bytes of packet fields are used for device address system.

  1. Data Link Layer

Most common data link layer functions should be done in this layer like other protocols. However at the moments only media access control is defined as Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA). The full frame structure and other link control mechanism have to be defined considering the characteristics of PLC. In near future, House Code will be provided to support the plug and play feature in LnCP home networks.

  1. Physical Layer

This layer is concerning the physical media transmission using Modulation/Demodulation. The specific modulation/demodulation scheme hasn’t been decided yet.

Fig.2 LnCP Packet Format

HOME NETWORKING DIGITAL TV

HNTV is implemented on real-time embedded OS with one serial communication interface that can be used in downloading program as well as in communicating with other LnCP devices. Nearly all of the command codes are dealt with in application layer and GUI is devised with XM graphical library that is used to make GUI for Digital TV. HNTV takes mainly master role and partly network manager role in LnCP networks. Whole layer of LnCP except for MAC and physical dependant areas are implemented. Since the communication module of HNTV is independent of other digital TV system, the communication with other appliances in home networks can be done without any interruption to the whole digital TV system.

The following shows the implementation structure of LnCP in HNTV. Each task performs a corresponding function in LnCP layer. Typically LnCP layer is devised with two tasks: LnCP SND Task and LnCP RCV Task. Those tasks communicate with application task using message queues. Application task delivers the proper information to GUI task through message queue to display the status and control information to the user.

Fig.3 Communication Structure in HNTV

At the moment HomeNet GUI in HNTV provides five major control panels with which user can see the status and control information. These are about air-conditioner, washing machine, microwave oven, refrigerator and Kimchi-refrigerator. Home Net UI has the extensibility. Thus, control panels will be expanded as the devices enter the home network.

CONCLUSION

LnCP is the event driven protocol that uses the special message set to control and monitor appliances in home network. Furthermore, it is interoperable with any other transmission technologies. Built on all those features of LnCP, Home Networking Digital TV has an ability of controlling devices and displaying the status of other devices. More works are remained in improving network manager features of HNTV.

REFERENCE

[1] Bill Rose, “Home Networks: A Standards Perspective”, IEEE Communication Magazine, Dec. 2001, pp 78 ~ 85.

[2] Technical Paper of LG Electronics Inc.,“Living Network Control Protocol (LnCP) ver1.1”, Nov. 2001.

[3] K. S. Lee, H. J. Choi, C. H. Kim, S. M. Baek, “A New Control Protocol for Home Appliances – LnCP”, proceedings of ISIE 2001, May 2001, pp 291~296.